Pixel solution A US study has found transistors made out of carbon nanotubes can produce the same brightness and colour intensity as standard silicon transistors, but use less power.

Currently organic light emitting diodes (OLEDs) are replacing LCDs as the standard screen technology in devices such as phones, TV and computer screens. They are lighter, faster and more power efficient than LCD, but they operate at higher voltages.

In the study, published today in Science, Dr Mitchell McCarthy of the University of Florida and coleagues demonstrate that transistors made out of carbon nanotubes could be an alternative.

Most OLED displays use a thin film transistor made out of silicon as their electrical foundation. The transistor powers a sandwich of organic materials layered between two metal plates, which pushes an electrical current through the stack of materials.

In a series of experiments McCarthy and colleagues showed that their carbon nanotube based transistors operated at lower voltages than silicon based transistors. That means they consume less power, without compromising brightness or colour intensity.

The power-size paradox

Dr Adam Micolich is an ARC Future Fellow at the University of New South Wales School of Physics, who is working on the electronic properties of semiconductor nanowires.

He says Mccarthy's team seem to have overcome a set of basic paradoxes in building and applying OLED technology.

"I think it's a nice way of solving the problems that they're having with OLED displays and getting them to operate with lower power," he says.

"One way to improve the power consumption properties of your transistor is to make the transistor a little bigger, and the light emitting element a little smaller," he says.

"But if you do that, then to get the same amount of light per area you've got be getting more light out of the individual light emitting elements. That means you have to put more current through them."

According to Micolich, one of the problems with existing OLEDs is that as more current flows through them they lose brightness and you shorten their lifetime.

"So there's an incentive to try and cut down the current you have to force through the pixels. And then you want to make your pixel bigger, but if you do that then you have to make your transistor smaller and you come back against this power problem," he says.

"So a really neat aspect of this paper is that they solve the transistor problem without costing themselves too badly in problems with the light emitting element."

Micolich says the use of carbon nanotubes helps "overcome some of the problems that have been around with silicon for a long time."

"If you talk to a fabrication engineer, they'll tell you that silicon is very hard to beat in real products. It's just such an established material to work with. But that's changing slowly."